The present invention relates to equipment for producing shaft information in an elevator shaft, in which a coded strip is arranged over the shaft height, wherein the code of the strip is readable by means of a sensor device arranged at an elevator car movable in the elevator shaft and is convertible into travel parameters of the elevator car.
Equipment for the generation of shaft information, by means of which the absolute position of the elevator car is determined, has become known from the U.S. Pat. No. 4,433,756. An extensible apertured strip tensioned over the shaft height is scanned by means of an optical reader arranged at the elevator car. The apertured strip has two tracks, wherein one track represents the binary coded car position and the other track has openings at regular intervals over the entire strip length. The first track is scanned by an optical reader and the second track by two optical readers and the direction of the movement of the elevator car is determined therefrom.
A disadvantage of this known equipment resides in the fact that the strip has to be supported at several points over the shaft height. It is further disadvantageous that temperature fluctuations have a direct effect on the accuracy of the shaft information. Moreover, the apertured strip is contaminated with oil-laden dust due to the air circulation prevailing in the elevator shaft, as a result of which problems and inaccuracies arise in the optical scanning of the perforations.
The present invention concerns a device for producing information related to a position of an elevator car in an elevator shaft. The device includes a toothed belt having a first length greater than a second length of a travel path of an elevator car in an elevator shaft in which the toothed belt is to be installed, the toothed belt having a plurality of teeth spaced along at least a portion of the first length, an encoder adapted to be mounted on the elevator car, the encoder having a toothed wheel for engaging the plurality of teeth, and at least one guide roller adapted to be mounted on the elevator car for engaging the toothed belt and urging the plurality of teeth into engagement with the toothed wheel. The toothed belt has spring characteristics for self-tensioning when installed in the elevator shaft. A pair of transverse beams adapted to be fixedly mounted at upper and lower positions in the elevator shaft are provided and opposite ends of the toothed belt are connected to associated ones of the transverse beams.
The toothed belt can have a marking on at least one side to enable a twist-free mounting in the elevator shaft and the marking can be a color of the at least one side. The encoder stores an absolute position of the elevator car in a non-volatile manner. The absolute positional information of the elevator car enable determination of the absolute position of the elevator car in the elevator shaft, the speed of the elevator car and the travel direction of the elevator car.
The advantages achieved by the device according to the present invention are substantially to be seen in the fact that the equipment is largely maintenance-free, cannot be contaminated and is constructed from usual commercial parts. In the case of power failure the equipment according to the present invention does not lose the positional information and learning travels after the power failure are not necessary. Moreover, the equipment replaces all non-safety-relevant shaft switches for producing shaft information. The toothed belt serving as an information transmitter is disposed in fixed engagement with the encoder, so that slipping between the toothed belt and encoder cannot occur. The toothed belt, which is tensioned over the shaft height at two ends, is simple to mount. Since the toothed belt has a reinforcement with spring characteristics, no additional tensioning elements in the form of, for example, tension springs are necessary for the mounting. The ends of the toothed belt can each be formed into a respective eye and be connected with the toothed belt by means of a clip. The eye loops around a cylindrical mount arranged in the shaft. Changes in the constructional body due to temperature or aging do not have any influence on the accuracy of the equipment according to the present invention, because the toothed belt is always tensioned and the level of a specific floor is always at the same tooth of the toothed belt.